1. Field of the Invention
This invention relates to the field of materials testing. More specifically, the present invention comprises a method and apparatus for toughness-testing corrugated high density polyethylene pipe.
2. Description of the Related Art
Corrugated high density polyethylene (“HDPE”) pipe is commonly used in many drainage applications. For example, corrugated HDPE pipe is widely used in highway drainage systems, storm water diversion and retention systems, agricultural drainage systems, and on-site wastewater systems. Corrugated HDPE pipe is a popular piping option because it is durable, flexible, lightweight, cheap and easy to install. HDPE is a relatively inert plastic and is resistant to mechanical abrasion. Because of its corrugated construction, corrugated HDPE pipe is also capable of withstanding many static and dynamic loading conditions. It has been used as a replacement for concrete pipe in many applications.
Corrugated HDPE pipe is also widely popular because it is easy to size and install. The pipe may be obtained in long lengths from the manufacturer. When smaller lengths are needed, it can easily be cut to any desired length. For applications where longer lengths of piping is needed, corrugated HDPE pipes can be effectively coupled together to create a water-tight and silt-tight seal.
Corrugated HDPE pipe has several common modes of failure. One commonly observed mode of failure involves “cracking” along corrugation fold lines under static or dynamic loading conditions. Cracking failures may be reduced by quality control. Although various testing procedures are generally available for strength-testing materials, none of the prior art methods are effective for evaluating the effect of static and dynamic loading conditions on corrugation fold lines. Thus, it is advantageous to provide a testing method specifically designed to evaluate the corrugation fold lines.